(Pro)renin receptor (PRR) is a newly discovered component of the renin-angiotensin system. The exact physiologic and pathologic functions of PRR are not established yet. Our preliminary studies in vitro and in vivo demonstrated that hyperglycemia increases PRR expression and activity, a process that is regulated by angiotensin AT1 receptor (AT1R), mainly via their heterodimerization. As a result of the interaction between AT1R and PRR there is upregulation of V-ATPase and Wnt3a expression and activity leading to renal inflammation fibrosis and albuminuria. In vivo intrarenal interstitia administration of PRR shRNA or Wnt3a shRNA reduced albuminuria, renal inflammation and morphologic changes associated with hyperglycemia. Based on these data, it is likely that PRR directly contributes to development of hyperglycemia-induced renal injury. The long-term goal of our research program is to elucidate the in vitro and in vivo novel mechanisms contributing to the regulation of PRR expression and function and evaluate the pathological significance of this receptor interaction with AT1R, vacuolar-ATPase (V-ATPase) and Wnt3a, and lead to development of hyperglycemia- induced renal disease. To achieve this goal, we will utilize a rationale and novel integrated approaches, consisting of in vivo studies utilizing combined knockdown of renal PRR, V-ATPase or Wnt3a and renal interstitial microdialysis technique in conscious normoglycemic and hyperglycemic streptozotocin- induced diabetes rats. These studies will be complemented by state-of-the-art in vitro cellular and molecular techniques utilizing siRNA, shRNA, EMSA, ChIP assays, and Laser Scanning Confocal FRET microscopy to rigorously test the proposed hypothesis. Based on our recent observations and preliminary data, the central hypothesis of this proposal is that in presence of hyperglycemia, PRR activity is increased by dimerization with AT1R leading to enhanced expression and activity of V-ATPase and Wnt3a signaling pathways to induce renal inflammation, fibrosis and albuminuria. We will pursue the following specific aims: Aim 1: To test the hypothesis that hyperglycemia increases PRR expression and activity and its heterodimerization with AT1R, leading to renal inflammation, fibrosis and albuminuria. Aim 2: To test the hypothesis that hyperglycemia- enhanced PRR activity mediates renal injury by increasing the expression and activity of V-ATPase. Aim 3: To test the hypothesis that hyperglycemia-enhanced PRR activity contributes to renal injury via increased expression and activity of Wnt3a. These studies are expected to identify novel pathophysiologic mechanisms related to PRR and could lead to development of new therapeutic strategies for treating hyperglycemia-induced renal disease.